In wiper apparatus for vehicles, an arm shank is pivotably supported at its proximal end portion on a vehicle body, an arm piece is attached to a distal end portion of the arm shank, and a wiper blade is mounted to the arm piece. Window glass of the vehicle is wiped with the wiper blade through pivoting movement of the ark shank.
The arm shank has a substantially U sectional shape defined by front and rear side walls and a ceiling or upper wall and thus has an inner space. Air flow produced by traveling of the vehicle (hereinafter referred to as “traveling wind”) hits the front wall of the arm shank, so that a turbulent air flow occurs in a space behind the front wall. The turbulent air flow hits the rear wall to produce high-frequency vibrations, which may resonate to produce relatively great air-cutting sound or wind noise.
In Japanese Patent Application Laid-Open Publication No. 11-43020 (JP 11-043020 A), for example, there is proposed a wiper apparatus which is designed to minimize or avoid production of undesired wind noise by forming the rear wall of the arm shank so as to have a lower height than the front wall of the arm shank. For this purpose, the rear wall is formed into a smaller width than the front wall or bent along its longitudinal side edge toward the front wall. With the rear wall of the arm shank having a smaller height than the front wall, the traveling wind can flow smoothly from the front wall toward the rear wall, which can minimize occurrence of a turbulent air flow in a space between the front wall and the rear wall.
However, in the wiper apparatus disclosed in JP 11-043020 A, the arm shank has a complicated shape because the rear wall of the arm shank has be formed into a smaller height than the front wall, which would result in low productivity of the wiper apparatus.